AUGUSTA, Maine — Maine Gov. John Baldacci has ordered flags to half-staff on Monday and Tuesday to honor the late Sen. Robert C. Byrd of West Virginia.

Byrd died early Monday at a Virginia hospital at age 92 after a Senate career that stretched more than a half-century. Baldacci, a fellow Democrat, described Byrd as “an institution in Washington and in the United States Senate” who bore witness to “great change and progress.”

Republican Sen. Olympia Snowe described him as “a distinguished, iconic legislator.” She said he served as “conscience and champion of Congress.”

Byrd held more leadership positions than any senator, serving at various times as Senate majority or minority leader, chairman of its Appropriations Committee, which makes key spending decisions, and finally president pro tempore, or third in line for the presidency.